Phosphorus-containing lubricating oil additives



Patented June 23, 1953 PHO SPHORUS CONTAINING LUBRICATING OIL ADDITIVES Alfred H. Matuszak, Jersey City, and Charles A. Weisel, Somerville, N. J assignors to Standard Oil Development Company, a corporation of Delaware N Drawing. Application October 1, 1948, Serial No. 52,394

3 Claims.

The present invention relates to phosphoruscontaining lubricating oil additives and also lubricants containing such additives whichhave exceptional properties which are highly useful in lubricating oil compositions and the like. The invention pertains more particularly to certain combined esters involving phosphorus, a monobasic acid radical, and. a polyhydric alcohol radical.

It has been suggested in the prior art that certain organic derivatives of acids of phosphorus, for example, the organic phosphates and phosphites such as tricresyl phosphates, tributyl phosphites, and the like, have certain useful properties in lubricating oils.

It is also known in the prior art that esters of certain polyhydroxy alcohols have some utility as rust inhibiting compounds, and the present invention is based upon the discovery that unexpected desirable properties may be obtained by combining organic-phosphorus radicals with such ester radicals. Some of the properties so obtained are extreme pressure load-carrying properties, rust, and other corrosion inhibiting properties, and the like. By combining these materials into a single molecule, the properties obtained are materially superior to those which can be obtained by a physical combination of the ingredients. The new types of esters have desirable properties in themselves "but the invention contemplates also their combination With oils such as mineral lubricating oil, synthetic oils, coating compositions, rust inhibiting slushing oils, and the like.

The esters which characterize the present invention may be prepared by reacting pentaerythritol, dipentaerythritol, polypentaerythritol, and the like, with a mono-basic acid and a phosphorus-containing acidic compound. The ester of the polyhydric alcohol and mono-basic acid is preferably prepared first either as a monoester or as a polyester. This ester is then subsequently treated with a phosphorus-containing acidic compound to produce the phosphate ester product disclosed herein. The mono-basic acid is preferably an aliphatic acid which may be saturated or unsaturated and is preferably of a chain length of 6 to 24 carbon atoms. Although a long chain acid having a single unsaturated bond such as oleic acid and its immediate homologs is preferred, other acids or mixtures of acids such as tall-oil acids or those acid mixtures derived from naturally occurring products may be employed without affecting appreciably the desired properties of the phosphate ester. The phosphorus-containing acidic compound may be 2 POCls, P015, PSCls, and the like, or mixtures of any two or more of these.

The method of preparing esters and the probable formulas of such esters are set forth in greater detail below. The esters are found to be efiective oiliness agents, anti-wear agents, extreme pressure additives, rust and other corrosion inhibitors, and they may have other desirable properties. They appear to be useful in preventing the sticking of piston rings in internal combustion engines and they also have some utility as pour point depressors, film strengtheners, viscosity index improvers, and detergents. The lighter compounds, i. e., those of lower molecular weight, may be used as ingredients of penetrating fluids, varnish removers, and the like. These material are useful also as sludge dispersers in internal combustion engine oils. For the above purposes, the proportions may vary but in general the combined esters of the present invention may be blended into base oils in concentrations as low as 0.01% by weight to as high as 10% by Weight or more. In some cases, it is desirable to market concentrates in mineral oil, for example, and in such cases the concentrations of the combined esters may be considerably higher, for example, 50% or more by weight, depending upon the solubility of the phosphorus-containing esters.

Although these materials are particularly useful for blending into mineral base lubricating oils, they may also be blended into petrolatums, lubricating greases, coating or slushing compounds, and into analogous oils and compositions based on synthetic lubricants such as the estsers of dibasic acids, polyalcohcl derivatives, and the like.

Since these materials involve the esterification of polyhydric compounds which may have several hydroxyl groups, the polyester compounds may be either monomeric or polymeric in nature. The invention contemplates also the use of mixtures of monomers or polymers or both. Also for some purposes a mono-hydric alcohol may be employed to form a part-of the ester linkages of the phosphorus-containing reagent. As previously suggested, the mono-basic acid is normally a monocarboxylic acid such as oleic, stearic, lauric, one of their homologs, a mixture of their homologs such as might be derived by the oxidation of petroleum products, or a mixture of acids obtained from naturally occurring products.

Pentaerythritol is a typical example of a polyhydric alcohol whose ester may be reacted with a phosphorus-containing acidic compound to produce a combined ester-of the type under con- 3 4 sideration. As mentioned previously, the mono- By this formula there is obtained a monophosbasic acid ester may first be prepared, after which phate mixed polyester. the ester may be reacted with a phosphorus- General types of monophosphate mixed polycontaining compound. For example, pentaerythesters are indicated in the following formulas: ritol mono-oleate may be reacted with POC13 to 011, 011,03 yield a mixed phosphate ester of pentaerythritol mono-oleate. The same reaction may be carried I out with PClz or PSC13. In the case of those OR OH OH reactions where hydrochloric acid is released in I the reaction, it is desirable to remove the HCl O=P(0CHzC-CH1O0O--R) and this may be done conveniently by employing HZOH a neutralizing agent such, for example, as pyri- CHOH dine. The following equations illustrate, respectively, monomeric phosphate polyesters, a poly- O=P OCH OHOOOR meric or cross-linked polyphosphate polyester, 0R moH Y H0 cH, --ooH=o0oo11H,z (HO0H7)3CCH1OOCC17H33 PO01; 8 1 8H1 CHOOCCHH P) C 2 CH2 \P/ O CH2-( 3OHzO0CCnHn (H) X CHaOH and a phosphate polyester prepared from pentaey is formula p p p p y r y rythritol monmoleate and POC13 and a monobe obtained. Analogous non-cyclic products also hydric alcohol ROH which is indicated in Equay e prepared. An examp e s d cated 111 tion 0 reacted with the phosphorus atom. the next formula.

R 01110 0 0-11 o 3 (CHiOH)! (3H1 0111011 0 (3H1 011,011 RCOOCHnCCH1O OCH2-(:3CH201-T OCH2AITCH1OOC-R ICHZOH 2 CHzOH O X CHaOH (X :21 number, preferably greater than one) A more general formula for the cyclic poly- Z 40 phosphate polyester is the following:

-R O=PO CHr-CCHzOOCCnHaa HOCHH: CHOOC CH1 OH: OCH: 5 CH 000 R and/or r EH20]; \P-/- 00112-0 o=r oom -0moooomam= g g H2011 CHIOH By the above reaction a monopho p P Y- ester compound may be obtained. g X

In general, several types of monophosphate omon polyesters can be prepared, having the following 1 lyp p M d P lyest r: general formulas;

/OCH: O= OCH:- O=PO CHTC'-OH:OOCR I! 0 I CZHa OCH: 011,011

E i? -oomtomooon O=P(OCH -CH1O0GR): 0 X CHZOH H1011 CHNH It will be noted that several of the compounds 0 R shown above contain free or unesterified hydroxyl groups. The number of such unesterified hy- CHZOH droxyl groups in any of the above polyester com- 5 pounds may be varied, or if desired, the polyester H OH may be completely esterified by properly regulat- B ing the ratio of the reactants. It will be under- ROE-H9001; (HOCHmC onlooconn stood, therefore, that the formation of many polyesters not shown in the above formula is possible and that the polyesters coming within C the scope of the invention are not limited by 0 2 0132011 these formulas. The reactions indicated may be 0R caused to proceed at various rates by changing Alcohol Treated MommeIf the reaction temperature which is normally kept \BCCPQW hydrocarbon radical I between 0 and 0., the exact operating tem perature being dependent to a large degree upon the reactivity of the phosphorus containing re- 1 actant or reactants. These polyester products are produced which contain phosphite and monobasic acid ester linkages.

.As previously described in connection-with Formulas B and 0- above, the polymeric or crosslinked as well as the mono-hydric alcohol treated polyester compounds may also be formed in reactions involving the. phosphorus-containing sul- 1 fides. The invention is not-limited to the compounds named, since many equivalent substances will suggest themselves to those skilled in the art.

Various modifications and combinations of the several reagents are possible.

The invention will be more fully'undertsood by reference to the following examples:

EXAMPLE 1 A mixed phosphate of a C8 oxo alcohol (prepared by combining an olefin with carbon monoxide and hydrogenating) and pentaerythritol mon0-oleate-was prepared as follows: To a constantly stirred mixture containing 135 parts by weight of pentaerythritol mono-oleate, 350 parts of benzene, 130 parts of Ce oxo alcohol and 127 3 :parts of pyridine there were added drop by drop 77,.parts of phosphorus oxychloride (P0013). The temperature was maintained below 10 C. while the POCls was being added. After addition 1 was completed, the mixture was permitted to "warm to room temperature after which it was refluxed for 3 hours. The mixture thereafter was thoroughly washed with water and the solvent benzene was stripped therefrom at 150 C. at a reduced pressure of 10 mm. This yielded in addition to the solvent 20 parts of the Ca oxo alcohol. The higher boiling residue, which amounted to 260 parts by weight, consisted of the mixed phosphate ester.

The mixed ester prepared as just described was evaluated for its rust inhibiting properties by employing it in various concentrations in a standard phenol extracted Mid-Continent lubricating oil of about 120 S. U. S. viscosity at 210 F. The test compositions so prepared were used as a crankcase oil in a standard single cylinder Wisconsin engine. After running the engine for eight hours with each of the test oils, the cylinder was removed from the engine and stored without any further treatment in a Tenney humidity cabinet in which the temperature was caused to vary between 72 and 90 F. and the relative humidity between 94 and 53% during each 24 hour cycle. Such conditions highly favor rusting and simu late a typical summer day in Cuba.

After five days storage under the warm humid conditions just described, the amount of rust which developed was determined and recorded in terms of percent of the total cylinder barrel area rusted. The base oil alone and the base oil with 1% by weight of pentaerythritol monooleate without any other inhibitor were evaluated for comparative properties along with the base oil containing, respectively, 0.25%, 0.5%, and 1% by weight of the ester. The results of these tests are tabulated as follows:

. 'Table I Percent Cyl- Oil Wisconsin Engine Rust 'I1ests-Blend figg gj g After 5 Days A 1 wt. percent Ester in Base Oil 2 B 0.5 wt. percent Ester in Base Oil 9 C. 0.25 wt. percent Ester in Base Oil 11 D 1 wt. percent Pentaerythritol Mono-0leate l0 in Base Oil. 1 E Base Oi1.(no added rust inhibitor) 35 These data show very clearly that the mixed phosphate ester composition prepared as described above greatly inhibits cylinderbarrel rusting when employed as an additive in a crankcase lubricating oil. In addition, this pentaerythritol mono-cleate Cs oxo alcoholphosphate appears to be a more effective rust inhibitor than the pentaerythritol lnono-oleate from which it is derived. Pentaerythritol mono-oleate itself has been considered a very effective inhibitor and the substantial superiority of the mixed ester prepared as above is noteworthy.

EXAMPLE 2 Table II LOAD CARRYING PROPERTIES or OILINESS AGENTS Shell 4-Ball Almen Mag. oa eig ts on Blend 30 Min., Carried, Wear Spot Gradual Dia., mm. Loading A. 2% Mixed Phosphate Ester 0.39 8

gilxample I) in Base Mineral l B 2% Commercial OilinessAgent 0.52 4

in Base Mineral Oil. 0. 2% Pentaerythritol Mono- 0.52 4

Oleate in Base Mineral Oil. 7 Base Mineral Oil 0.65 23 The foregoing data indicate that esters prepared according to the present invention posses superior properties in anti-wear and film strength to either the standard commercial oiliness agent or to the pentaerythritol mono-oleate ester from which the mixed ester was derived.

In general the invention includes the phosphorus containing esters (including thiophosphorus esters) of alcohols which are also partially esterified by a monobasic acid, especially a monobasic fatty acid having 6 to 30 carbon atoms, preferably 8 to 24 carbon atoms. The composition by itself, as well as an ingredient of lubricating oil is contemplated.

More specifically, the invention contemplates the mixed phosphate and/or phosphite esters of alcohol partially esterified with a monobasic acid, preferably an organic acid, especially a fatty acid of 6 to 30 carbon atoms. The somewhat narrower range of 8 to 24 carbon atoms in the fatty acid chain is preferred for some purposes. The rust inhibiting composition may have the formula CH2 O=PO CHz-CCH2O 0 OR where R is an alkyl group of 6 to 30 carbon atoms, but the invention comprehends various modified formulas, as indicated above, and also comprehends their use in varying proportions, from as little as 0.01% to 50% by weight, based on the total composition, in lubricants such as lubricating oils, greases, etc. The higher percentages will be used, for example, in concentrates, the normal amounts to be employed in finished products being generally within the range of 0.01 to 10%, by weight, based on the total composition. For use in internal combustion engines, the preferred range is from 0.1% to 5%, based on the weight of the finished lubricant.

The invention comprehends not only the mixed esters in the technical sense (e. g. esters of a polyhydric alcohol, partially esterified by an acidic derivative of phosphorus and partially esterified by an organic acid) but also mixtures of simple or mixed esters. Thus, in reacting a phosphorus containing reagent and an organic acid with alcohol, a rather complex mixture may be obtained. The various formulas given above are probably somewhat idealized. When pentaerythritol monooleate is reacted with POC13, for example, the product may or may not be properly described by a specific formula. However described, this product, and the variations mentioned above, are found useful for the purposes of this invention.

Thus a composition derived from a monohydric alcohol, such as a C8 oxo alcohol or equivalent, a polyhydric alcohol such as pentaerythritol or its equivalent, a phosphorus-containing acidic material such as POCls or the alternative compounds mentioned above, and a fatty acid such as oleic acid or the like is a highly desirable product, and is the essence of this invention, although chemical formula is not susceptible of exact definition. Lubricants, preferably but not necessarily of mineral base, are improved by these products as previously described.

What is claimed is:

1. As a new composition of matter, a phosphorus-containin ester prepared by reacting together pentaerythritol mono-oleate and a C1 to C monohydroxy aliphatic alcohol at temperatures not above reflux with a phosphorus-containing material selected from the group which consists of POCls, P015, and PSCla, in the presence of pyridine and a solvent, said ester being stripped of water and of said pyridine and solvent after reaction is substantially complete.

2. Composition according to claim 1 wherein the alcohol is a Ca oxo alcohol.

3. Composition according to claim 1 wherein the phosphorus-containing material is POCla.

ALFRED H. MATUSZAK. CHARLES A. WEISEL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,365,291 Prutton Dec. 19, 1944 2,373,811 Cook Apr. 17,1945 2,407,279 Hull Sept. 10, 1946 2,408,744 Engel Oct. 8, 1946 2,413,353 Hunter Dec. 31, 1946 2,422,630 Musselman et al. June 17, 1947 2,426,691 Jenkins Sept. 2, 1947 2,446,944 Morgan Aug. 10, 1948 

1. AS A NEW COMPOSITION OF MATTER, A PHOSPHORUS-CONTAINING ESTER PREPARED BY REACTING TOGETHER PENTAERYTHRITOL MONO-OLEATE AND A C1 TO C30 MONOHYDROXY ALIPHATIC ALCOHOL AT TEMPERATURES NOT ABOVE REFLUX WITH A PHOSPHORUS-CONTAINING MATERIAL SELECTED FROM THE GROUP WHICH CONSISTS OF POCI3, PCI5, AND PSCI3, IN THE PRESENCE OF PYRIDINE AND A SOLVENT, SAID ESTER BEING STRIPPED OF WATER AND OF SAID PYRIDINE AND SOLVENT AFTER REACTION IS SUBSTANTIALLY COMPLETE. 